Alternative harvest control rules for achieving sustainable fisheries under the revised Fisheries Act in Japan: case studies in two Japanese sardine stocks

Harvest control rules (HCRs) are intended to provide total allowable fishing mortality or catches in response to the current stock status. This study presents candidates for HCRs that can be applied to two Japanese sardine stocks in Japan. Our simulation study suggests that some alternative HCRs outperform currently adopted HCRs in terms of robustness to potential uncertainty with similar performance in future average catches and stock levels. We also show that the future projection method considering only future recruitment stochasticity, which is currently used in the domestic stock assessment, underestimates future risk probability. Recognizing the uncertainty in future risk evaluation, it is important to select HCRs based on the performance relative to the HCRs that are known to be robust to uncertainty.